Feeder Size for multi-motor circuits

[United36]

So I have panel with4 circuits. Each circuit has (5) 20 HP motors. I can do the multi-motor calc for each branch circuit just fine (1.25 x largest + 1.0 x others). But when I am sizing the feeder I am not sure how to do it. I think I have three options.

Option 1: Largest of 20 motors X 1.25 and remaining 19 motors x 1.0
Option 2: Largest of the (4) multi-motor circuits x 1.25 and the other (3) x 1.0
Option 3: All (4) circuits just x 1.0.

Any thoughts on the right way to do this per code?


Any help would be greatly appreciated!

 

[augie47]

IMO, Option 1

 

[petersonra]

So I have panel with4 circuits. Each circuit has (5) 20 HP motors. I can do the multi-motor calc for each branch circuit just fine (1.25 x largest + 1.0 x others). But when I am sizing the feeder I am not sure how to do it. I think I have three options.

Option 1: Largest of 20 motors X 1.25 and remaining 19 motors x 1.0
Option 2: Largest of the (4) multi-motor circuits x 1.25 and the other (3) x 1.0
Option 3: All (4) circuits just x 1.0.

Any thoughts on the right way to do this per code?


Any help would be greatly appreciated!

Unless I am completely misunderstanding your situation only options 1 and 2 are code compliant. Option 2 is code compliant but might result in a larger size conductor than the minimum required. It is also not guaranteed to be code compliant for all possible situations. It would be in this case though.

There is a chance option 3 would be code compliant in this particular case.

Option 1 is the way to do the calculation that will always work.